Is the Canon EF 16-35mm f/4L IS USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 28mm f/4.0 test image. Observe the contrast and resolution of these results.
Is the Canon EF 16-35mm f/4L IS USM Lens set to 28mm f/4.0 sharper than the Sony FE 16-35mm F2.8 GM Lens set to 16mm f/3.2? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.